Information on the SI within this reference is primarily based
on three NIST publications, which are available in electronic (acrobat pdf)
format. (If you do not have this software, you may wish to
obtain
it free from Adobe.)

Guide to the SI, with a focus on usage and unit
conversions:NIST Special Publication 811, 2008 Edition, by Ambler Thompson and Barry N. Taylor.Guide for the Use of the International System of Units (SI)

This
publication, abbreviated SP 811, has been prepared by NIST to provide
assistance in the use of the SI. The topics covered by SP 811 include:

NIST policy on the
use of the SI in NIST publications.

Classes of
SI units, those SI derived units that have special names and symbols, and the
SI prefixes that are used to form decimal multiples and submultiples of SI
units.

Those units
outside the SI that may be used with the SI and those that may not.

Rules and
style conventions for printing and using quantity symbols, unit symbols, and
prefix symbols, and for spelling unit names.

Rules and
style conventions for expressing the results of measurements and the values of
quantities.

Definitions
of the SI base units.

Conversion
factors for converting values of quantities expressed in units that are mainly
unacceptable for use with the SI to values expressed mainly in units of the SI.

Guide to the SI, with a focus on history:NIST Special Publication 330, 2008 Edition, Barry N. Taylor and Ambler Thompson, EditorsThe International System of Units (SI)

This
publication, abbreviated SP 330, is the U.S. version of the English language
text of the 8th edition of the brochure Le Système International
d'Unites (SI). The 8th edition of the brochure, which is the current
definitive reference on the SI, was published in the French language in 2006 by
the International Bureau of Weights and Measures (BIPM, Bureau International
des Poids et Mesures).
Except for very minor differences, SP 330 is identical to the
English-language text that follows the official French language text in the two
BIPM publications.
The BIPM SI Brochure, and thus SP 330, contains
Resolutions and Recommendations of the General Conference on Weights and
Measures (CGPM, Conférence Générale des Poids et
Mesures) and the International Committee for Weights and Measures (CIPM,
Comité International des Poids et Mesures) on the SI. Also
included is explanatory material, as well as relevant extracts from the
International Standards of the International Organization for Standardization
(ISO) for the practical use of the SI.

Guide to the SI, with a legal focus:Federal Register notice of May 16, 2008, 73 FR 28432-28433Interpretation of the International System of Units for the United States

This notice
restates the interpretation of the SI for the United States by the Department
of Commerce.
As provided by U.S. law, the metric system of measurement to be used in the
United States is the SI as established by the General Conference on Weights and
Measures and interpreted or modified for the United States by the Secretary of
Commerce. The Secretary has delegated this authority to the Director of the
National Institute of Standards and Technology.

Diagram of SI unit relationships:

This
schematic diagram illustrates how the 22 SI
derived units with special names and symbols are related to the seven SI base
units. Versions optimized for printing are available.

History of the SI, with a focus on the BIPMNBS Special Publication 420, 1975 Edition, C. Page and
P. Vigoureux, EditorsThe International Bureau of Weights and Measures 1875-1975

This
publication, abbreviated SP 420, gives the history of the first century
(1875-1975) of the International Bureau of Weights and Measures (BIPM,
Bureau International des Poids et Mesures), including the history of the
Convention du Mètre (Meter Convention) and the SI. It is out of print,
and not available online.

Weights and measurements in the United States, with a focus on
history:NBS Special Publication 447, 1976 Edition, Louis E. Barbrow and Lewis V. JudsonWeights and Measures Standards of the United States, a brief history

This
publication, abbreviated SP 447, provides a brief history of U.S. weights and
measures from the founding of the country to about 1975. It includes copies of
the notices published in the Federal Register of the United States that give
the relationships between various customary units of weights and measures and
SI units. It is out of print, but available online in this PDF version.

Legal note: The Adobe Acrobat software is identified above in
order to assist users of this information service. In no case does such
identification imply recommendation or endorsement by the National Institute of
Standards and Technology.